A mechanical seal, an example of a sliding component, is evaluated in its performance by a leakage rate, a wear rate, and torque. In conventional techniques, by optimizing the seal materials and the sliding face roughness of mechanical seals, the performance is increased to achieve low leakage, long life, and low torque. However, due to growing awareness of environmental problems in recent years, a further improvement in the performance of mechanical seals has been demanded, and technology development beyond the limits of the conventional techniques has been required.
Under such circumstances, as one used in an oil seal device for a rotating component such as a turbocharger, for example, a known one includes a rotating shaft rotatably placed in a housing, a disk-shaped rotor rotating with the rotating shaft, and a disk-shaped stationary body that is fixed to the housing and abuts on an end face of the rotor to prevent the leakage of oil from the outer peripheral side to the inner peripheral side, the stationary body having an abutment surface provided with an annular groove that generates positive pressure by the centrifugal force of fluid, to prevent the leakage of oil from the outer peripheral side to the inner peripheral side (see Patent Document 1, for example).
Another known one in a rotating shaft seal device for sealing toxic fluid, for example, includes a rotating ring with a rotating shaft and a stationary ring mounted to a casing, one of the rotating ring and the stationary ring having a sliding face provided with a spiral groove for drawing liquid on the low-pressure side toward the high-pressure side by the rotation of the rotating ring, with an end on the high-pressure side being in a dead-end shape, to prevent the leakage of sealed fluid on the high-pressure side to the low-pressure side (see Patent Document 2, for example).
Another known one, as a face seal structure suitable for sealing a drive shaft of a turbocharger against a compressor housing, for example, has one of a pair of seal rings working together provided as a rotating component, and the other provided as a stationary component, the seal rings each having a sliding face formed substantially radially, and forming, between the sliding faces, a seal gap for sealing an area provided outward of the sliding faces against an area provided inward of the sliding faces during operation, at least one of the sliding faces being provided with a plurality of circumferentially spaced recessed portions effective for feeding gas, the recessed portions extending from one peripheral edge of the sliding face toward the other peripheral edge, inner ends of the recessed portions being radially spaced from the other peripheral edge of the sliding face, to seal a non-gas component in a gas medium containing the non-gas component (see Patent Document 3, for example).